Effects of O, H and N passivation on photoluminescence from porous silicon

A simple but effective passivation method for porous silicon (PS) has been developed. Immersion of as-etched PS in dilute (NH4)(2)S/C2H5OH solution fo llowed by ultraviolet light irradiation in air can lead to an enhancement o f photoluminescence (PL) up to more than 20 times. Infrared absorption and Auger electron spectroscopic measurements show that the formation of SiH(O- 3), Si-O-Si and Si-N bonds are formed during the post-treatment process. Ho wever, the PL intensity cannot be enhanced if the solution-treated sample i s exposed to the laser beam in vacuum. It is thus concluded, that the PL en hancement can be attributed to the presence of compact passivation films co nsisting of the oxides and the nitride on both external and internal surfac es of the sponge-like PS samples. (C) 2001 Elsevier Science B.V. All rights reserved.